The homespun folk-country songs of the late Kate Wolf form the basis for An Unfinished Life, a new choral work that premiered this week by the California Redwood Chorale. But not in the way fans are accustomed to hearing them.

"This is not a medley, not a series of songs that follow one another," clarifies New York–based composer Randall Keith Horton. "It's a choral setting that blends the songs—sometimes three or even four are happening at the same time—to help tell Kate's story."

A former Sonoma County resident, Horton met Wolf when she agreed to sing his "Petaluma Suite" with a small local orchestra he led in 1980. "She refused to take what little money I was offering," he recalls. "I never forgot that."

After learning of Wolf's 1986 death of leukemia at age 42, Horton set out to craft a musical appreciation, a project interrupted at length by his work as an arranger for the Duke Ellington Orchestra. He completed it in 2009.

As he studied Wolf's songs, Horton says he "started finding themes—of mountains, of dreams, of love, of rivers, of friendship." One song provided the title for his 20-minute composition, and Horton freely admits to reinterpreting Wolf's lyrics. "All the allegory that refers to nature I have taken as musical metaphor that tells her own biography," he explains.

Chorale founder Gerry Schulz describes Horton's music as "a dreamlike state. It's woven where the men may be singing part of one song and the women another, and then out of that texture will come Bonnie Brooks with her extraordinary voice."

The entire piece is accompanied by just mandolin and guitar, the latter played by Wolf's one-time husband and musical collaborator Don Coffin. Brooks, a soprano, is featured as the solo voice of the songwriter.

The 50 singers—all volunteers from throughout the Bay Area—have been rehearsing since before Christmas, says director Robert Hazelrigg, who found the new work unexpectedly difficult. "This," he says, "has been a significant challenge for us."

Among the 13 songs threaded through Unfinished Life are such favorites as "Red-Tailed Hawk," "Friend of Mine," "The Lilac and the Apple," Midnight on the Water" and, as a summary closing statement, "Give Yourself to Love." Yet the lines Horton cites most often are drawn from "Across the Great Divide," which he has recast not as a crest of mountain peaks, but the chasm separating life and death.

"The line of the story is one of reconciliation," Horton reflects, "but the story is love."